1. Field of the Invention
The present invention relates to a vane pump and a vapor leakage check system.
2. Description of Related Art
A known vane pump compresses and discharges fluid by rotating a rotor with vanes driven by a motor. For example, JP-A-2005-98285 (corresponding to U.S. Pat. No. 7,234,344) discloses a vapor leakage check system having one such vane pump. The vane pump depressurizes or pressurizes the interior of a fuel tank. Thereby, the system checks leakage of fuel vapor from the fuel tank. A performance of the vane pump is important because the performance of the vane pump has significant influence on a performance of the system.
A conventional vane pump has a pump chamber and a rotor with vanes in the pump chamber. The pump chamber is made of a first casing and a second casing, which are joined to each other and mounted to a mounting portion of the motor by a screw. The rotor with vanes is rotated in the pump chamber to compress and discharge fluid.
An airtightness of the pump chamber of the conventional vane pump, that is, a sealing performance between the first casing and the second casing greatly affects a pump performance (e.g., discharge pressure). For example, when a flatness of a contact face between the first casing and the second casing is low, it may be difficult to make the first casing and the second casing to be in close contact with each other. In this case, a gap may be generated in the contact face between the first casing and the second casing, and fluid may leak from the pump chamber through the gap. Thus, the pump performance may become low.